1. Field of the Invention
The present invention relates to a process ofr producing beta (.beta.)-carotene and novel intermediate compounds useful for the process.
.beta.-carotene is a valuable compound used as a food additive and the like.
2. Description of the Related Art
It is known that .beta.-carotene is synthesized for example by the following processes.
(A) A process comprising reacting by way of acetylenediol. See Helv. Chim. Acta., 39(27), 249 (1956). ##STR2##
(B) A process comprising reacting vitamin A phosphonium salt with hydrogen peroxide. See Japanese Patent Publication No. 10659/1984. ##STR3##
(C) A process comprising synthesizing from vitamin A phosphonium salt and vitamin A aldehyde. See German Patent 1,068,709 (1958). ##STR4##
(D) A process comprising synthesizing from vitamin A sulfone and vitamin A halide. See Japanese Patent Application Laid-open No. 5543/1973. ##STR5##
The above syntheses for .beta.-carotene have the following drawbacks.
Process (A) synthesizes .beta.-carotene from the starting compound .beta.-ionone while requiring so many reaction stages;
Process (B) requires triphenyl phosphine in an equivalent amount based on the mole of vitamin A and must use a hazardous peroxide;
Process (C) must separately synthesize vitamin A aldehyde from vitamin A which is unstable when exposed to heat or acid; and
Process (D) must separately synthesize vitamin A halide which is extremely unstable when heated.
Accordingly an object of the present invention is to provided an improved process for producing .beta.-carotene easily and from starting materials that are inexpensive and readily available.
Another object of the present invention is to provide a novel intermediate product used advantageously for the above improved process.
Other objects and advantages of the present invention will become apparent from the following descriptions.